1. Field of the Invention
The present invention relates to a blasting method and apparatus provided with an recovery system for abrasives used the blasting process, and more particularly to a blasting method including a recovery method of the abrasives, especially fine particle abrasives as a system for recovering the abrasives in the blasting and a blasting apparatus used for this processing, the blasting apparatus provided with an abrasive recovery system executing the method.
In more detail, the present invention relates to a blasting method and a blast processing apparatus (hereinafter, referred to as “blasting apparatus”) which can prevent fine abrasives (hereinafter, referred to as “abrasives”) and cut scraps including crushed abrasives by the blasting process from being attached to an article to be processed (hereinafter, referred to as “workpiece”), which is preferably adapted to a so-called blasting using the abrasives, and a thin-film solar cell panel in accordance with the processing method.
Further, the inventor of the present invention focused on the blasting process which has not been suggested, tried, experimented or exemplified as a means which might be applied in a scribing method for the thin-film solar cell panel. More detailedly, in the present invention, it is intended to provide a blasting method including a recovery step of fine abrasives and cut scraps without any mask (a cover fixed on a surface to preventing a part of the predetermined surface from processing) as well as a cleaning process of the workpiece after the blasting process by a blasting apparatus provided with an abrasive recovery system which is preferably used for a processing of the thin-film solar cell panel.
In the present invention, a concept of the abrasives includes a coarse particle as well as the fine particle. In JISR6001, a particle size distribution of the coarse particle is defined, and the particle size distribution up to the particle size F60 (indicated so in JIS) can be used. A typical particle size in F60 is 230 μm, however, hereinafter, the fine particle means a particle of #400 or more, or a particle with an average particle diameter 30 μm or less.
2. Description of the Related Art
As a processed example of the workpiece, there is experimentally referred to a gravity type blasting apparatus 60 which has not been conventionally employed, and a description will be given of it with reference to FIG. 7. The blasting apparatus is provided with a cabinet 61 forming a processing chamber inside thereof, for processing the workpiece (not shown) carried in the cabinet 61 through the intermediary of a carry-in port 63 by disposing a blast gun 62 having an ejection nozzle 62 within the cabinet.
In general, a recovery cycle of the abrasive in the blasting apparatus is configured as follows. That is, a lower portion of the cabinet 61 is formed into an inverse pyramid shape, a hopper 68 is formed at the lower portion, and a lowest end of the hopper 68 is communicated with an upper portion of a recovery tank 70 for recovering the abrasives, installed at an upper portion of the cabinet 61 through the intermediary of a conduit 65.
Further, the recovery tank 70 mentioned above is a so-called cyclone for separating the cut scraps from the abrasives. If a leading end of the conduit 65 is connected to an inflow port 73 of the recovery tank 70 through the intermediary of a communication pipe 75, and an inside of the recovery tank 70 is sucked by a dust collector (not shown) provided with a wind discharging machine through the intermediary of a connecting pipe 74 and a discharge pipe 67, the abrasives and the cut scraps within the cabinet has been transferred into the recovery tank 70 together with an air current through the intermediary of the communication pipe 75, the cut scraps are recovered by the dust collector at a time of falling down while turning along an inner wall of the recovery tank 70, and the reusable abrasives are collected in a bottom portion of the recovery tank 70 and pressure-fed to the blast gun 62 having an ejection nozzle 62 through the intermediary of an abrasive feeding pipe 64.
As mentioned above, the reusable abrasives can be ejected by the ejection nozzle of the blast gun together with the newly charged abrasives as occasion demands.
Thereafter, the recovering cycle mentioned above is repeated.
As mentioned above, in the conventional blasting apparatus, the abrasives ejected within the processing chamber is fed into the recovery tank 70 by a negative pressure generated by the dust collector, then recovered. However, in the case of using the fine particle having a small particle diameter, since a surface area of each fine abrasives are larger with respect to its weight in comparison with a general abrasive, the fine abrasives have a property tending to firmly attaching or agglutinating to the workpiece or the like. Accordingly, once the fine abrasives are attached to the workpiece and the inner wall of the processing chamber, it is hard to remove it even if an inside of the processing chamber is sucked by the negative pressure or an air blowing or the like is applied to the workpiece.
Accordingly, the workpiece to which the blasting is applied by such fine abrasive requires a step for removing the fine abrasives attached to a surface thereof by cleaning it with a washing water after the blasting.
As mentioned above, in the blasting using the fine abrasive, taking into consideration the fact that once the fine abrasives are attached to the workpiece or the like, it is hard to remove it, there has been proposed to recover the fine abrasives before they are attached to the workpiece or the other places.
As one example of such structure, in a blasting apparatus 80 shown in FIG. 8, it has been proposed that one end of a processing duct 81 is provided with a blast gun 91 having an ejection nozzle 91 ejecting abrasives, the other end of the processing duct 81 is communicated with a suction duct 83 sucking abrasives by a negative pressure, the processing duct 81 is provided with a blast chamber 82 in a front side of an ejection current of the abrasives, a side wall of the blast chamber 82 is provided with an insertion port 84 inserting a workpiece W in a direction which is approximately orthogonal to the ejection current of the abrasives, and an intake port 85 as an intake gap for sucking an ambient air is formed between an inner periphery of the insertion port 84 and an outer periphery of the workpiece W, whereby the fine abrasives ejected to the workpiece in the blast chamber is immediately sucked from the suction duct, and the abrasives are prevented from scattering to the processing chamber by an air blow generated by the ambient air sucked from the intake gap (see Japanese Patent LOPI No. H09-300220).
In this case, since the blasting using the fine abrasive can be carried out at a high precision, it can be expected to be utilized in various fields. As one example, there can be considered a utilized field which is substitute for the currently utilized laser processing in a scribing (a fluting) carried out in a manufacturing step of a thin-film solar cell panel.
In this case, the scribing carried out in the manufacturing step of the thin-film solar cell panel is generally carried out by the laser at the present, however, as shown in FIGS. 9A and 9B, it is required a step for removing a thin film layer from a glass substrate in a range of width within several mm to ten and several mm in a peripheral edge portion, before attaching a glass cover after forming thin film layers such as a back electrode, a light absorbing layer, an emitter, a transparent electrode and the like which are required for the thin-film solar cell, on the glass substrate. Therefore, even in the case that a metal frame made of aluminum or the like is attached to the peripheral edge portion after attaching the glass cover, it is possible to prevent a short circuit between the metal frame and the peripheral edge by removing the thin film layer at the peripheral edge portion as mentioned above.
In this case, the scribing by means of the laser carried out in the manufacturing step of the thin-film solar cell panel is also carried out in the case of dividing the thin-film solar cell panel into each of the cells as well as the example mentioned above.
The laser processing apparatus mentioned above is expensive, a lot of initial investment is necessary, and a comparatively high running cost is required because a nitrogen gas is consumed in a nitrogen gas laser which is generally used for this kind of work.
Accordingly, if the scribing mentioned above can be carried out by a blasting apparatus which is inexpensive in comparison with the laser apparatus and a method called as a blasting which can comparatively hold down the running cost, it is advantageous in a cost competitive power in a market.
However, in the case that the scribing mentioned above is carried out by the blasting using the fine abrasives, since the ejected abrasives are attached to the workpiece, it is necessary to remove the abrasives attached as mentioned above, however, the fine abrasives are hard to be removed once it is attached to the workpiece, as mentioned above, and can not be easily removed by sucking the processing chamber by means of the dust collector or applying the air blow to the workpiece.
Accordingly, if the fine abrasives attached to the workpiece as mentioned above is going to be removed, it is required to wash the workpiece with water or the like after the blasting, however, in the case that the workpiece is the thin-film solar cell mentioned above, it is impossible to wash it with the washing water, and there has been no effective means for removing the fine abrasives attached thererewith.
Further, in the case of carrying out the cut by the blasting apparatus, since the abrasives ejected by an ejection hole of a blast gun bombarded onto the workpiece as shown in FIG. 10, and diffuses to all the directions, such as, 360 degree along a surface of the workpiece together with the air current feeding the abrasives, the workpiece is cut not only in a surface on which bombarded with the abrasives but also in the periphery.
Accordingly, if the scribing as mentioned above is going to be carried out by the blasting, it is necessary to previously protect the surface of a non-cut portion by sticking the mask material on the surface in such a manner that the surface to be left without being removed is not cut.
However, in the case that the thin-film solar cell panel mentioned above is employed as the workpiece, each of the layers formed on the glass substrate is comparatively brittle, and there is a risk that the thin film layer is peeled off from the glass substrate due to a shock at a time of sticking and peeling a mask material, when it is stuck or peeled off after processed.
As mentioned above, in the blasting using the fine abrasives, since the abrasives are firmly attached to the workpiece so as to be hard to be removed, and it is necessary to stick the mask material for defining the cut range, the blasting can not be applied to the workpiece which can neither washed nor stuck by the mask material such as the thin-film solar cell panel, in spite that it is excellent in terms of the cost in comparison with the scribing by the laser.
In this case, in the apparatus brought on as '300220 mentioned above, it is intended to recover the fine abrasives before they are attached to the workpiece, however, the workpiece which is applicable here is limited to a cylindrical-shaped workpiece or a linear workpiece, on the basis of a structure shown in FIG. 8, and can not be applied, for example, to a plate-like two-dimensional workpiece vertically separates the processing chamber into two.
Further, in the structure described in '300220 mentioned above, it is essential to stick the mask material if it is intended to form a groove having a fixed width with respect to the workpiece, and it is impossible to use for the scribing of the thin-film solar cell panel in this regard.
In this case, in the present specification, a description will be given by exemplifying the thin-film solar cell panel formed into the plate-like two-dimensional shape as one example of the workpiece, however, the same problem mentioned above is generated even in the workpiece made of various materials which can neither be washed with the washing water nor be stuck by the mask material, without being limited thereto.
Further, even in the workpiece which can be washed and stuck by the mask material, there is an advantage that productivity is improved and a working cost can be reduced as far as it is possible to omit the washing and the sticking of the mask.
As the foregoing, there is a serious defect that the abrasives or the like can not be peeled off and fallen away by an after blow and a water washing is required once the abrasives or the like is attached to a surface to be processed of the workpiece W in the related art mentioned above.
Accordingly, an object of the present invention is to overcome the above disadvantage in providing a blasting method and a blasting apparatus including an abrasive recovery system which can easily recover the abrasives or the like before being attached to the workpiece even in the case of using the fine abrasives, accordingly can make the step of the (water) washing or the like for removing the fine abrasives after the blasting unnecessary without generating the attachment thereof, and can carry out a fluting or the like at a fixed cut width without sticking a mask material to the workpiece which is moved relatively.